The invention described herein relates generally to photon calorimeters, and more particularly to improved photon calorimeters of simple design and economical construction.
A calorimeter is an apparatus used for measuring quantities of heat. A well known diagnostic technique, for measuring the intensity and spectral characteristics of a beam of photon radiation, is to pass the beam into or through a photon calorimeter and measure the temperature rise induced thereby. In a known type of photon calorimeter, separate thin disks, comprised of various materials, are stacked and clamped closely together. The atomic numbers and arial densities of the individual disks are specifically chosen to somewhat provide tailored radiation absorption properties for the calorimeter. The disks are typically comprised of pure single-element metals, such as beryllium, gold and lead, to name a few, or structural materials of known composition, such as various alloys and plastics. Temperature rise is measured by thermocouples whose measuring junctions are distributively positioned throughout the clamped disk structure of the calorimeter. This type of calorimeter has many disadvantages. For example, the natural and unavoidable gaps that always exist between individual disks, appreciably prolong the time it takes for the calorimeter to equilibrate in temperature. This effect is worsened by the thermal warping of the individual disks that accompanies heat deposition within the disk system. Another very serious disadvantage of this calorimeter is that the amount of spectral tailoring that it can provide is extremely limited, because the disks comprising the calorimeter are limited in number and elemental composition. Inadequate spectral tailoring, in atomic composition, reduces the efficiency of this calorimeter and even makes it incapable of performing some measurements.
Martin, in U.S. Pat. No. 4,321,824 issued Mar. 30, 1982, discloses a high energy laser target board having an array of disk calorimeters spread around the surface of the board to receive laser energy. The energy striking any disk is sensed by a pair of thermal leads connected to the back side of the disk, and the voltage across the leads is amplified and sent to a recording system.
A method and apparatus for measuring radiant energy is taught by Zimmerer in U.S. Pat. No. 4,522,511 issued June 11, 1985. Relatively high energy levels of coherent radiation are caused to impinge upon an absorber surface. Energy from the radiation is transferred from the surface to a fluid coolant in thermal association therewith. The energy carried away by the coolant is measured, preferably, by a thermopile.
It is apparent that there is a need for improved photon calorimeters that equilibrate in temperature more quickly, and provide a better spectral tailoring capability, than presently existing photon calorimeters. It would be advantageous if these improved photon calorimeters were structurally rugged and relatively inexpensive to fabricate.